Statistics of an Unstable Barotropic Jet from a Cumulant Expansion
Low-order equal-time statistics of a barotropic flow on a rotating sphere are investigated. The flow is driven by linear relaxation toward an unstable zonal jet. For relatively short relaxation times, the flow is dominated by critical-layer waves. For sufficiently long relaxation times, the flow is turbulent. Statistics obtained from a second-order cumulant expansion are compared to those accumulated in direct numerical simulations, revealing the strengths and limitations of the expansion for different relaxation times.
© 2008 American Meteorological Society. (Manuscript received 3 May 2007, in final form 17 October 2007) We thank Greg Holloway, Paul Kushner, Ookie Ma, and Peter Weichman for helpful discussions. This work was supported in part by the National Science Foundation under Grants DMR-0213818 and DMR-0605619. It was initiated during the summer 2005 Aspen Center for Physics workshop "Novel Approaches to Climate," and JBM and TS thank the Center for its support.
Published - MARjas08.pdf